This invention relates to an illuminated spirit level which can be used either as a simple level or as a leveling device in other equipment such as surveying equipment. Conventional spirit levels which are of simple and inexpensive construction comprise a support body which provides a surface to be placed on an object and a bubble tube provided within the body which is generally elongate and positioned with its longitudinal axis either along the length of the surface or transverse thereto so that a gas bubble within the liquid in the bubble tube can be positioned centrally of the bubble tube when the support surface is horizontal or vertical.
Spirit levels of this type are inexpensive and readily available and widely used. However they have a serious disadvantge in that it is very difficult or impossible to use the spirit level in low levels of illumination when the bubble cannot readily be seen.
Alternative forms of level indicating devices have been proposed to overcome this problem of illumination. Generally these solutions provide complicated electrical sensing of the position of a bubble or other floating object. These solutions have found little acceptance generally in the trade probably because they are expensive and complicated in comparison with the simple bubble tube arrangement which is fully satisfactory except in relation to this problem of illumination.